Fuel cell power plant for mobile unit

ABSTRACT

A fuel cell power plant is provided for a mobile unit. The mobile unit is provided with a drive device ( 29 ) driving the mobile unit when supplied with electrical power. The power plant comprises a fuel cell ( 21 ) generating power when supplied with fuel, a battery ( 27 ) charged with power generated by the fuel cell, a power regulation device ( 31 ) selectively distributing power from the fuel cell ( 21 ) and the battery ( 27 ) to the drive device ( 29 ), and a controller ( 33 ) for controlling running operations. The controller ( 33 ) estimates the energy required to activate the fuel cell ( 21 ), and controls the power regulation device ( 31 ) when the energy required to activate the fuel cell is greater than or equal to a determination value so that the fuel cell is not activated and power from the battery ( 27 ) is supplied to the drive device ( 29 ). In this manner, it is possible to prevent unnecessary power consumption during startup operations.

FIELD OF THE INVENTION

[0001] This invention relates to a fuel cell power plant for a mobileunit and in particular, it relates to activation operations therefor.

BACKGROUND OF THE INVENTION

[0002] A fuel cell and a battery mounted in a hybrid fuel cell vehicleis known as a conventional fuel cell power plant for a mobile unit byJP-A 2000-315511. A drive motor for running the fuel cell vehicle drivesthe vehicle when supplied with electrical power from a battery orelectrical power generated by the fuel cell.

[0003] At vehicle startup, when the driver switching the ignition switchto the ON position, the fuel cell is activated in order to allow vehicleoperation. However at startup, the fuel cell is not able to commencepower generation immediately. Consequently the vehicle supplies power tothe drive motor from the battery. Thereafter, when power generation bythe fuel cell is enabled, power is supplied from the fuel cell.

SUMMARY OF THE INVENTION

[0004] An amount of power must be supplied in order to activate the fuelcell. In particular, when a fuel reformer is provided which reforms fueland supplies a gas containing hydrogen to the fuel cell, a large amountof power is required to activate the fuel cell. The required power toactivate the fuel cell differs depending on the operating conditions.For example, the power consumption undergoes a conspicuous increase whenfuel cell activation is commenced under low temperature conditions.

[0005] In particular, during short-term running conditions in which thevehicle is operated for an extremely short time, vehicle operation maybe terminated in the period when power generation by the fuel cell mayor may not be enabled. Consequently even if the fuel cell is activated,it is often the case that power will be not supplied from the fuel cell.Consequently power is unnecessarily consumed by activating the fuelcell.

[0006] It is therefore an object of this invention to suppress powerconsumption by operating the vehicle without activating the fuel cellwhen large amounts of energy are required to activate the fuel cell.

[0007] Furthermore when the vehicle is operated for only a short periodof time, unnecessary power consumption can be avoided by not activatingthe fuel cell.

[0008] In order to achieve above the objects this invention is providedwith a fuel cell power plant for a mobile unit. The mobile unit has adrive device for running the mobile unit when supplied with power. Thepower plant comprises a fuel cell generating power when supplied withfuel, a battery charged with power generated by the fuel cell, a powerregulating device selectively distributing the power from the batteryand the fuel cell to the drive device and a controller for controllingvehicle operation. The controller estimates the energy required toactivate the fuel cell and sets a determination value corresponding to arelatively small amount of energy within the energy required to drivethe fuel cell. When the estimated energy required for activation isgreater than or equal to the determination value, the fuel cell is notactivated and the power regulating device is controlled in order tosupply power from the battery to the drive device.

[0009] The details as well as other features and advantages of theinvention are set forth in the remainder of the specification and areshown in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a block diagram of a first embodiment of this invention.

[0011]FIG. 2 is a flowchart describing an activation control routine fora fuel cell according to the first embodiment.

[0012]FIG. 3 shows the characteristics of the relationship between thetemperature of the fuel reformer and the activation energy.

[0013]FIG. 4 is a flowchart showing an activation control routine for afuel cell according to a second embodiment.

[0014]FIG. 5 shows the characteristics of the relationship between theexternal temperature and the activation energy of the reformer and theelapsed time after the after the stopping the reformer until theignition key switched to the ON position.

[0015]FIG. 6 is a flowchart showing an activation control routine for afuel cell according to a third embodiment.

[0016]FIG. 7 shows the characteristics of the relationship of runningmode reference parameters and the limiting value for a running mode.

[0017]FIG. 8 is a flowchart showing an activation control routine for afuel cell according to a fourth embodiment.

[0018]FIG. 9 shows the characteristics of the relationship between stateof charge (SOC) and the determination value.

[0019]FIG. 10 is a flowchart showing an activation control routine for afuel cell according to a fifth embodiment.

[0020]FIG. 11 is a flowchart showing an activation control routine for afuel cell according to a sixth embodiment.

[0021]FIG. 12 shows the characteristics of the relationship between theactivation energy of the fuel cell and the activation completion time.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] In order to describe the invention in greater detail, thepreferred embodiments will be outlined below with reference to theaccompanying figures.

[0023]FIG. 1 is a block diagram of the structure of a fuel cell vehicleaccording to a first embodiment of the invention. This fuel cell vehicleis a hybrid fuel cell automobile mounting a power source comprising astorage battery and a fuel cell having a fuel reformer.

[0024] The fuel reformer 1 generates a reformate gas containing hydrogenfrom a fuel containing a hydrocarbon. For example when methanol is usedas the fuel, methanol as the fuel stored in a methanol tank 5 iscombined with water from a water tank 9 in order to generate a reformategas containing hydrogen from steam reforming reactions.

[0025] The fuel reformer 1 may be supplied with air as required from acompressor 15 in order to generate a reformate gas by partial oxidationof methanol.

[0026] The reforming reaction performed in the fuel reformer 1 may bedivided into steam reforming reactions which are endothermic and partialoxidation reactions which are exothermic.

[0027] The fuel cell 21 is provided with an anode and a cathodeelectrode. Reformate gas from the fuel reformer 1 is supplied to theanode electrode and air from the compressor 15 is supplied to thecathode electrode. The fuel cell 21 generates power from electrochemicalreactions using oxygen in the air and hydrogen in the fuel gas.

[0028] A combustor 3 is provided downstream of the fuel cell 21. Thecombustor 3 is disposed adjacent to the fuel reformer 1. Since theoxygen in the air and the hydrogen in the reformate gas supplied to thefuel cell 21 are not completely consumed, the excess of the reformategaseous discharge containing hydrogen and discharged air containingoxygen are combusted in the combustor 3. The combustor 3 transfers theresulting heat of combustion to the fuel reformer 1 where it is used inorder to vaporize water and methanol. For this purpose, air from thecompressor 15 is combusted as required together with methanol from themethanol tank 5 in the combustor 3.

[0029] A motor 29 driven by supplied electric power is provided in orderto drive the fuel cell vehicle. The motor 29 is connected to drivewheels 30 and the vehicle is driven by the rotations of the motor 29.

[0030] A battery 27 is provided separately from the fuel cell 21. Whenthe fuel cell vehicle decelerates,

[0031] The battery 27 is charged with the excess amount of powergenerated by the fuel cell and power generated by operating the motor 29as a generator when the fuel cell vehicle decelerates. Conversely whenthe output of the fuel cell 21 is insufficient to satisfy the powerconsumption of the compressor 15, the fuel reformer 1 and the combustor3 or to meet the required power for running the motor 29, the battery 27supplies the deficit of the fuel cell output.

[0032] A power regulating device 31 is provided in order to selectivelydistribute the power from the fuel cell 21 and the battery 27 to themotor 29 and the auxiliary devices (compressor 15, fuel reformer 1,combustor 3 and the like).

[0033] A controller 33 is provided to control the distribution of powerby the power regulating device 31.

[0034] The controller 33 comprises a central processing unit (CPU), aRAM, a ROM and an input/output interface and may comprise a plurality ofmicrocomputers. Signals are input into the controller 33 from a ignitionswitch 36 which indicates startup of vehicle operation, an acceleratorpedal sensor 37 which outputs a signal in response to the depressionamount (accelerator opening) of an accelerator pedal 35, a vehicle speedsensor 38 which outputs a signal in response to the vehicle speed, a SOCsensor which detects the level of charge (state of charge) in thebattery 27, a temperature sensor 40 which detects the temperature aboutthe fuel cell and temperature sensor 41 which detects the temperature ofthe atmosphere.

[0035] In this invention, particularly at startup of fuel cell vehicleoperation, the controller 33 performs a control routine for fuel cellactivation in order to avoid unnecessary power consumption.

[0036] At startup of vehicle operation, the fuel cell 21 must beactivated and time is required until power generation by the fuel cellis enabled. The time required varies in response to the operatingconditions and normally a relatively large amount of power is consumeduntil activation is completed.

[0037] In the period until power generation by the fuel cell 21commences, the motor 29 is driven by power supplied from the battery 27.However particularly when the operating time is short, for example whenvehicle operation is terminated before the fuel cell 21 actuallyinitiates power generation, activating the fuel cell 21 merely resultsin adverse effects on fuel efficiency due to unnecessary consumption ofelectric power.

[0038] Consequently the controller 33 estimates the energy required toactivate the fuel cell 21 based on the operating conditions at thattime. The fuel cell 21 is activated only when the activation energy issmall. In other cases, power consumption resulting from activation issuppressed since the activation control routine is not performed.

[0039] A control routine performed by the controller 33 will bedescribed with reference to FIG. 2. FIG. 2 is performed only on oneoccasion when the ignition switch (IGN) is switched from the OFF to theON position.

[0040] In the control routine as shown in FIG. 2, the activation energyrequired to activate the fuel cell is estimated based on the temperatureof the fuel reformer 1.

[0041] In a step S10, the temperature of the fuel reformer 1 (whichcorresponds to the temperature of the fuel cell) detected by thetemperature sensor 40 is read. In a step S20, the energy required toactivate the fuel cell is calculated by looking up a table as shown inFIG. 3 based on the detected temperature.

[0042] The energy required to activate the fuel cell as shown in FIG. 3decreases as the fuel cell temperature increases. This is due to thefact that it is necessary for the temperature of respective componentsin the fuel cell to increase to a predetermined temperature during fuelcell activation. Consequently the required amount of heat for activation(activation energy) decreases as the temperature before activationincreases.

[0043] In the step S30, a determination value Q is compared with theenergy required to activate the fuel cell 21. The determination value Qis set to a value corresponding to the energy required for activation onrestarting operation when the fuel cell 21 is sufficiently warmed up.This represents the situation when fuel efficiency does not greatlydeteriorate and little energy is required for activation even if thefuel cell 21 is activated in a short-term operating mode. For example,the value is set to approximately 10% of the maximum value foractivation energy assuming activation of the fuel cell in an extremelycold state. In this manner, an optimal value can be set based onempirical, experimental or statistical data.

[0044] When the energy required for activation of the fuel cell 21 isless than the determination value Q, the routine proceeds to a step S40and the fuel cell 21 is activated. More precisely, an activation processfor the fuel cell 21 is performed using an activation flag in which thefuel cell activation flag has a value of one (initial setting=0).

[0045] An example of the activation process for the fuel cell 21 will bedescribed below.

[0046] When the activation routine is commenced, the fuel cell 21 isbypassed by connecting the inlet of the combustor 3 with the outlet ofthe fuel reformer 1. Thereafter exothermic reactions resulting frompartial oxidation reactions are performed by supplying air and fuel tothe fuel reformer 1. The reformate gas from the fuel reformer 1 issupplied to the combustor 3 and H2, CO, HC in the reformate gas arecombusted in the combustor 3. Once the temperature of the fuel reformer1 reaches a predetermined temperature, autothermic reactions areperformed by supplying water to the fuel reformer 1 or steam reformingreactions are performed by stopping the supply of air. When the detectedtemperature in the fuel reformer 1 shows that the stream reformingreactions have stabilized, supply of a reformate gas (H2 rich gas) tothe fuel cell 21 is commenced in order to commence power generation bythe fuel cell 21. Thereupon activation of the fuel cell 21 is completed.

[0047] Conversely when the energy required to activate the fuel cell 21is greater than or equal to the determination value Q, the routineproceeds from the step S30 to a step S50 and the fuel cell 21 is notactivated (fuel cell activation flag=0).

[0048] When the fuel cell 21 is being activated or is not activated, thevehicle operates in an EV running mode and is only supplied with powerfrom the battery 27.

[0049] As shown in FIG. 3, when the temperature of the fuel cell (fuelreformer) is a low temperature T1, the energy required for activation isgreater than the activation temperature Q. Thus the fuel cell (fuelreformer 1) is not activated. In contrast, at a temperature T2, sincethe energy required for activation is smaller than the determinationvalue Q, the fuel cell 21 is activated.

[0050] Thus in this embodiment, when the fuel cell vehicle startsoperating, if the energy required for activating the fuel cell 21 islarge, the fuel cell 21 is not operated. In particular, when theoperation is completed in a short time, it is possible to avoidunnecessary power consumption by the battery since energy is notrequired for activating the fuel cell 21.

[0051] Another embodiment of the invention will be described withreference to the flowchart in FIG. 4 which shows the operation of thecontroller 33.

[0052] The point of difference from the first embodiment as shown inFIG. 2 is that, the steps S12, S22 of the second embodiment in FIG. 4are different from the steps S10, S20 in FIG. 2.

[0053] That is to say, in the step S12, an elapsed time is read. Thisperiod is the time from stopping the fuel cell 21 on an immediatelyprevious occasion by turning the ignition switch to the OFF positionuntil the ignition switch is turned back to the ON position. Thetemperature detected by the temperature sensor 40 is read. The elapsedtime is measured by a timer provided in the controller 33. Instead ofthe temperature sensor 40, a temperature sensor may be provided to readthe external temperature and this detected external temperature may beread.

[0054] In a step S22, the energy required for activating the fuel cell21 is calculated by looking up a map as shown in FIG. 5 based on theelapsed time and the external temperature.

[0055] When the elapsed time is held constant, the energy required foractivation as shown in FIG. 5 decreases as the external temperatureincreases. When the external temperature is held constant, the energyincreases as the elapsed time increases.

[0056] This is due to the fact that it is necessary for the temperatureof respective components such as the fuel reformer 1 to increase to areference temperature during activation of the fuel cell 21.Consequently the required amount of heat (activation energy) foractivating the fuel cell 21 decreases as the external temperatureincreases. Furthermore after the operation of the fuel cell 21 isstopped on an immediately previous occasion, the energy required foractivation increases as the time increases until a subsequent startupoperation. This is due to the fact that the temperature of the fuelreformer falls in response to the elapsed time after stopping the fuelcell 21 and results in a corresponding increase in the amount of heatrequired for reactivation.

[0057] According to this embodiment, it is possible to perform anaccurate estimation of the energy required for activation by estimatingthe energy required for activating the fuel cell 21 based on the elapsedtime from stopping the fuel cell 21 on an immediately previous occasionuntil the ignition switch is placed in the ON position on a subsequentoccasion or based on the external temperature at that time.

[0058] A third embodiment of this invention will be described withreference to the flowchart in FIG. 6 which shows the operation of thecontroller 33.

[0059] The flowchart shown in FIG. 6 supplements the first embodiment asshown in FIG. 2 or the second embodiment as shown in FIG. 4. That is tosay, after the control routine shown in FIG. 2 has been performed, theflowchart in FIG. 6 is executed at a period of 10 milliseconds forexample. However it is stopped after the fuel cell has once beenactivated.

[0060] In the step S60 as shown in FIG. 6, the value of the fuel cellactivation flag is checked. This value is set as a result of theignition switch being turned from OFF to ON in FIG. 2.

[0061] When the fuel cell activation flag has a value of zero, theroutine proceeds to a step S70 and subsequent steps. In the steps S70,S80, S90, determination of the running mode is performed. That is tosay, in the step S70, the running mode determination parameters areread. The running mode determination parameters are defined herein as:

[0062] {circle over (1)} actual running time after switching ignitionswitch to ON position

[0063] {circle over (2)} actual running speed

[0064] {circle over (3)} required amount of power for running

[0065] {circle over (4)} power consumption by battery

[0066] {circle over (5)} depression speed of accelerator pedal

[0067] The actual running time [sec] in {circle over (1)} above may bemeasured by a timer provided in the controller 33. The actual runningspeed [m/s] in {circle over (2)} above is detected by a vehicle speedsensor (not shown). The required amount of power [kW] for running in{circle over (3)} above is detected based on the opening of theaccelerator detected by the accelerator pedal sensor 37. The powerconsumed by the battery (kW) in {circle over (4)} above is calculatedfrom the SOC (state of charge) [%] which is a value representing thebattery capacity. The speed of depressing the accelerator pedal 35[opening/s] in {circle over (5)} above is calculated based on theaccelerator opening detected by the accelerator pedal sensor 37.

[0068] In the step S80, the five running mode determination parametersabove are used separately in order to determine whether the vehicle isoperating in a normal running mode or whether it is operating in ashort-term operating mode. The respective determinations are performedbased on FIG. 7.

[0069] The left end in the uppermost panel in FIG. 7 (first step) is theminimum value for actual running time (for example 0 sec). The thresholdvalue dividing short-term operation running mode from normal runningmode is basically determined in the following sequence.

[0070] (1) A map is prepared on the basis of simulations or runningtests in company premises in order to determine the threshold time forthe short-term operation running mode or normal running mode withrespect to respective vehicle running conditions (external temperature,humidity, load or the like).

[0071] (2) The threshold time (map value) is corrected based on theactual vehicle operating conditions.

[0072] In the second panel in FIG. 7, the left end represents a minimumactual running speed (for example 0 m/s). The right end is the maximumactual running speed. The threshold speed between the short-termoperation running mode and normal running mode is determined based onthe power consumption amount at that time and the general runningpattern. The actual running speed is assumed to be an instantaneousvalue.

[0073] The left end of the third panel of FIG. 7 is the minimum requiredamount of power (for example 0 kW) for running. The right end is themaximum required amount of power for running. The maximum requiredamount of power for running is determined from the maximum load runningpattern for the vehicle. In the same manner, the left end in the fourthpanel in FIG. 7 represents the minimum power consumption amount by thebattery (for example 0 kW) and the right end is the maximum powerconsumption amount by the battery. The maximum power consumption amountby the battery is determined in response to the battery capacity.

[0074] The left end in the lowermost panel of FIG. 7 represents theminimum accelerator pedal depression speed (for example 0 opening/s) andthe right end represents the maximum accelerator pedal depression speed.

[0075] The reason for why the accelerator pedal depression speed is usedinstead of the accelerator pedal depression amount and why a normalrunning mode is determined when the value thereof is greater than orequal to the threshold value is as follows. A large depression speed onthe accelerator pedal 35 represents strong fluctuation in the load onthe vehicle. Consequently when the load undergoes strong fluctuation,the load on the battery 27 increases due to the increase in thefrequency of a charging/discharging operation by the battery 27. Thuswhen such load fluctuation occurs frequently, the fuel cell 32 isactivated in order to reduce the load on the battery 27 resulting fromcharging and discharging operations (normal running mode).

[0076] In this manner, when the actual running time is short, when theactual running speed is low, when the required power for running oramount of power consumed by the battery is low or when the speed ofdepressing the accelerator pedal is low, a short-term operation runningmode is determined. In contrast, when the actual running time is long,when the actual running speed is high, when the required power forrunning or amount of power consumed by the battery is large or when thespeed of depressing the accelerator pedal is high, a normal running modeis determined. The respective threshold values in FIG. 7 differdepending on the size of the vehicle.

[0077] In the step S90 in FIG. 6, it is determined whether the vehicleis in either running mode. When there is one running mode determinationparameter, if short-term operation running mode is determined, theroutine proceeds to a step S100 and the fuel cell 21 is not activated(fuel cell activation flag=0). When short-term operation running mode isnot determined, the routine proceeds from the step S90 to a step S110and the fuel cell 21 is activated (fuel cell activation flag=1).

[0078] When the ignition switch is switched from the OFF position to theON position, even when the fuel cell 21 has not been activated due tothe fact that the energy required for activation is greater than thedetermination value Q (steps S30, S50 in FIG. 2), the reformer 1 may beactivated (step S90, S110 in FIG. 6) when normal running mode isdetermined from the running mode determination parameter thereafter.

[0079] Actually since five running mode determination parameters areused, in the step S90, it is checked whether or not short-term operationrunning mode has been determination with respect to all the five runningmode determination parameters. When it is determined with respect to allthe five running mode determination parameters that the vehicle isrunning in short-term operation running mode, the routine proceeds to astep S100 and the fuel cell 21 is not activated.

[0080] In contrast, when even one of the five running mode determinationparameters shows that the vehicle is not operating in short-termoperation running mode, the routine proceeds from the step S90 to thestep S110 and the fuel cell 21 is activated. This is due to the factthat when even one of the five running mode determination parametersdetermines normal running mode, there is the possibility that the fuelcell 21 will not be activated before the capacity of the battery 27reaches a lower limiting value if the vehicle continues to operate inshort-term operation running mode. In order to prevent this type ofproblem, the fuel cell 21 is activated when any one of the running modedetermination parameters corresponds to normal running mode.

[0081] Consequently after placing the ignition switch in the ONposition, it is determined at a fixed period whether the running mode isnormal running mode or short-term operation running mode based on therunning mode determination parameters. The activation or non-activationof the fuel cell 21 is controlled on the result of that determination.Consequently the activation or non-activation of the fuel cell 21 can becontrolled in response to the running mode. This allows improvement toactual fuel efficiency and prevents reductions in performance.

[0082] However the method of determining the running mode is not limitedto that described above. For example, learning control can be used tostore a date/time running pattern comprising any one of a calendar 57A,a clock 57B, a GPS 57C (see in FIG. 1) or a combination thereof. Thus itis possible to determine either short-term operation running mode ornormal running mode according to the stored date/time running pattern.The date/time running pattern is a running pattern specific to thedriver determined on the date, day of the week or time period. Forexample, when the fuel cell vehicle is used for delivering goods, in aweekday time period, it is clearly the case that the vehicle willfrequently operate in a short-term operation running mode due toperforming deliveries to high-density housing areas. In this case,learning control stores short-term operation running mode as the modefor the delivery time period. Consequently in that time period,short-term operation running mode is immediately determined withoutperforming a determination of the running mode and the vehicle continuesoperation without activating the fuel cell 21.

[0083] A fourth embodiment of this invention will be described withreference to FIG. 8.

[0084] The flowchart in FIG. 8 is substituted for the flowchart in FIG.2 and FIG. 4 of the first and second embodiments.

[0085] The point of difference from the first and second embodimentsresides in the step S120 and the step S130 in FIG. 8. That is to say, avalue for SOC showing the state of charge of the battery 27 is read fromthe output of a SOC sensor 39 at a step S120. Thereupon the routineproceeds to a step S130 and the determination value Qs for the energyrequired to activate the fuel cell 21 is calculated by looking up atable as shown in FIG. 9 based on the value for the SOC.

[0086] When the determination value Qs as shown in FIG. 9 is larger thanthe lower limiting value SOCmin, it takes the same value as thedetermination value Q in the third embodiment. When SOC is less than orequal to the lower limiting value SOCmin, the determination value Qs isa value which corresponds to the maximum value Qmax for the assumedenergy required for fuel cell activation.

[0087] Consequently when the value of SOC in FIG. 8 is less than thelower limiting value SOCmin, the determination value Qs for the energyrequired for activation takes a maximum value Qmax for the assumedenergy for activation. At this time, in a step S30, since the energyrequired to activate the fuel cell 21 is always less than thedetermination value Qs, the routine proceeds from the step S30 to thestep S40 and the activation of the fuel cell 21 is ensured.

[0088] Even when operating for a short time, if the SOC falls to a levelat which the battery fails (that is to say, SOC reaches SOCmin), thevehicle can not operate while the fuel cell 21 is being activated. Inorder to prevent this type of problem, a residual battery charge isdesignated which is sufficient to drive the vehicle only using the motor29 while the fuel cell 21 is being activated.

[0089] The steps S10 and S20 in FIG. 8 represent the steps S10, S20 inFIG. 2 or the steps S12, S22 in FIG. 4. That is to say, in the step S10in FIG. 8, the calculation parameters for the energy required for fuelcell activation are read (the temperature of the fuel cell in the firstembodiment, the external temperature and the elapsed time from stoppingthe fuel cell to switching the ignition switch to the ON position in thesecond embodiment). In the step S20 in FIG. 8, the energy required foractivation is calculated based on the parameters (using the controlroutine in the first embodiment, a table as shown in FIG. 3 is lookedup, using the control routine in the second embodiment, a map as shownin FIG. 5 is looked up).

[0090] Thus in the present embodiment, since the determination value forthe energy required for activation is varied in response to the SOC ofthe battery 27, it is possible to prevent the vehicle not being able tobe driven by the motor 27 as a result of the residual battery chargebeing consumed during activation of the fuel cell 21.

[0091]FIG. 10 shows a fifth embodiment of this invention.

[0092] The flowchart in FIG. 10 corresponds to the flowchart in FIG. 6.The control routine shown in FIG. 10 is commenced when the ignitionswitch is switched from an OFF position to an ON position. The routineis repeated at a period of 10 milliseconds and terminated afteractivation of the fuel cell 21 is completed.

[0093] The point of difference from the third embodiment is that thesteps S140, S150 and S160 are introduced in place of the step S60 inFIG. 6.

[0094] That is to say, a running mode selection switch 51(see in FIG.1)is provided in the driver's compartment in the fifth embodiment inorder to allow selection of normal running mode or short-term operationrunning mode.

[0095] In the step S140, it is determined whether the driver hasselected either normal running mode or short-term operation running modeon the basis of the switch signal. If the driver selects normal runningmode, the routine proceeds to a step S110 and the fuel cell 21 isactivated (fuel cell activation flag=1).

[0096] On the other hand, when short-term operation running mode isselected, the routine proceeds to a step S150, and the SOC of thebattery 27 is read. In the step S160, this value for the SOC is comparedwith a determination value A.

[0097] For example, when the short-term operation running mode isselected by the driver, the determination value A corresponds to a SOC(fixed value) at which there is the possibility of the vehicle notoperating due to battery failure if the vehicle is operated only withpower from the battery.

[0098] Although the determination value A must be derived empirically,experimentally or statistically, 10-15 mode running which is anoperation test mode may be substituted and used in the calculation ofthe determination value A.

[0099] When SOC is less than or equal to the determination value A, itis determined that the vehicle will not operate due to battery failurewhen running on battery power. In this case, the routine proceeds to astep S110 and the fuel cell 21 is activated. However in order to avoidstopping the vehicle while running, it is preferred that running iscommenced after activation of the fuel cell 21 has progressed to a levelallowing vehicle running to be maintained or that when running iscommenced after power generation by the fuel cell 21 commences.

[0100] When SOC is greater than the determination value A, the residualbattery charge is determined to be a value which at least allowsshort-term operation running after the fuel cell 21 is activated from acold state until power generation commences. Thereupon the routineproceeds from the step S160 to the step S70 and the same process asshown in FIG. 3 with reference to the third embodiment is performed.

[0101] In this embodiment, when the driver selects normal running modewith the running mode selection switch, the running time using onlybattery power is shortened by immediately activating the fuel cell 21and thus it is possible to reduce the energy consumption from thebattery 27.

[0102] When the driver selects short-term operation running mode, thecurrent SOC state is determined. When running is performed only usingbattery power, operation in short-term operation running mode is onlyallowed when vehicle operation will not result in battery failure.Consequently it is possible to avoid a reduction in the residual batterycharge.

[0103] A sixth embodiment will be described with reference to FIG. 11.

[0104] The flowchart shown in FIG. 11 is substituted for the flowchartin FIG. 10 in the fifth embodiment.

[0105] The point of difference from the fifth embodiment resides in themethod of handling the running mode selection switch signal and in thefact that new steps S170, S180, S190 and S200 are added.

[0106] That is to say, in the step S140, the signal from the runningmode selection switch 51 is checked to determine whether the driver hasselected a running mode or whether either running mode has not beenselected.

[0107] The control routine when the driver has selected the normalrunning mode is the same as that described with respect to the fifthembodiment. The routine proceeds to a step S110 and the fuel cell 21 isactivated.

[0108] When the driver selects the short-term operation running mode,the routine proceeds to the steps S170, S180 from the step S140, and theenergy required for activation stored in the step S20 in FIG. 2 is read.This value is used in order to calculate a running power amount E[Wh]during activation of the fuel cell 21.

[0109] The calculation of the running power amount E during fuel cellactivation is as follows.

[0110] Firstly, the period until completion of the activation of thefuel cell 21 is calculated by looking up a table as shown in FIG. 12based on the energy required for activation of the fuel cell 21. Thenthe operation in this period is taken to be a 10-15 mode running. Thusthe amount of power consumed when running on the motor 29 in 10-15 modeduring the period until activation of the fuel cell 21 is completed canbe measured or calculated on the basis of experiment. In this manner,when relationship of the fuel cell activation completion time to energyconsumption during that time is set in a predetermined table, it ispossible to calculate the running power amount E during fuel cellactivation by looking up the table based on the reformer activationcompletion time.

[0111] The relationship between the power consumption by auxiliarydevices in order to activate the fuel cell 21 and the fuel cellactivation completion time can be calculated experimentally and set in atable. Thus the running power amount E during fuel cell activation canbe calculated more accurately by adding this value to the power consumedwhen running only on the motor 29.

[0112] In a step S190, a consumption ratio of the battery 27 when thebattery 27 uses a running power amount E during fuel cell activation iscalculated as SOC-E[%]. The consumption ratio SOC-E is compared with acurrent value for SOC in a step S200. When the consumption ratio SOC-Eis greater than or equal to the current value SOC, since vehicleoperation without immediately starting the fuel cell 21 will result inbattery failure, the routine proceeds to a step S110 from the step S200and the fuel cell 21 is immediately activated (fuel cell activationflag=1).

[0113] In this case, it is possible to ensure prevention of batteryfailure during vehicle operation if running is not commenced until thevalue for SOC is greater than the consumption ratio SOC-E.

[0114] In contrast, in a step S200, when the consumption ratio SOC-E isless than the value for SOC at that time, it is determined that it ispossible to continue short-term operation running using only the batterypower. Thereupon the routine proceeds to the step S100 and the fuel cell21 is not activated (fuel cell activation flag=0).

[0115] On the other hand, in the step S140, when the driver has notselected either running mode from the two running modes, the routineproceeds to the step S70 and subsequent steps. In the same manner as thefifth embodiment, the content of the running mode parameters isdetermined and it is determined whether or not to activate the fuel cell21.

[0116] When short-term operation running mode is determined in a stepS90, the routine proceeds to the step S170 and subsequent steps. As aresult, even when the driver has not selected either running mode, whenshort-term operation running mode is determined as a result of therunning mode determination (steps S70, S80 and S90), if the value forthe battery consumption ratio SOC-E is smaller than the current valuefor SOC, the routine proceeds to the step S110 from the step S200 andthe reformer 1 is activated. In this manner, it is possible to ensureprevention of battery failure during short-term operation running.

[0117] In this embodiment, the running mode during fuel cell activationand the running mode after completion of fuel cell activation aredetermined in addition to the short-term operation running mode. As aresult, the driver can be made aware of the selected running mode by apanel display or voice display 55 (see in FIG. 1) advising the driver ofthe three respective running modes.

[0118] This embodiment has described the activation of the fuel cellincluding whether or not the fuel reformer is activated as an example ofa fuel cell provided with a fuel reformer. However the invention is notlimited in this respect. The invention can be applied in the same mannerwith respect to whether or not to activate a fuel cell in a solid oxidefuel cell generating power by internal reforming reactions or a solidoxide fuel cell generating power directly from fuel using electrodereactions.

[0119] Although methanol has been described as the fuel supplied to thefuel reformer, the invention is not limited in this respect and propanegas, natural gas, naphtha gas or other hydrocarbon fuels may be used.

[0120] In the above embodiments, the fuel cell power plant for a mobileunit has been described with respect to application to a vehicle.However it is also possible to apply the invention to a ship orindustrial machinery.

INDUSTRIAL APPLICABLE

[0121] The present invention can be applied to the running control for afuel cell vehicle.

1. A fuel cell power plant for a mobile unit, the mobile unit providedwith a drive device(29) driving the mobile unit when supplied withelectrical power, the power plant comprising: a fuel cell(21) generatingpower when supplied with fuel; a battery (27)charged with powergenerated by the fuel cell; a power regulation device(31) selectivelydistributing power from the fuel cell and the battery to the drivedevice; a controller(33) functioning to estimate the energy required toactivate the fuel cell; set a determination value corresponding to arelatively small amount of energy in comparison to the energy requiredto drive the fuel cell; and control the fuel cell and the powerregulation device so that the fuel cell is not activated and power fromthe battery is supplied to the drive device when the estimated energyrequired to activate the fuel cell is greater than or equal to thedetermination value.
 2. The power plant as defined in claim 1, whereinthe controller(33) activates the fuel cell(21) when the estimated energyrequired to activate the fuel cell is less than the determination value.3. The power plant as defined in claim 1 or claim 2, wherein thedetermination value is set to a value corresponding to approximately 10%of the maximum value of the energy required to complete activation ofthe fuel cell(21) under cold conditions.
 4. The power plant as definedin claim 1, further comprising a sensor (40) for detecting thetemperature of the fuel cell (21); and wherein the controller(33)estimates the energy required to activate the fuel cell based on thetemperature of the fuel cell.
 5. The power plant as defined in claim 1,further comprising a timer for measuring time; and wherein thecontroller(33) estimates the energy required for activation of the fuelcell(21) based on the time from stopping the fuel cell on an immediatelyprevious occasion to activating the fuel cell on the present occasion.6. The power plant as defined in claim 1, further comprising asensor(41) for detecting an external temperature; and wherein thecontroller (33)estimates the energy required for activating the fuelcell(21) based on the external temperature.
 7. The power plant asdefined in claim 1, further comprising a SOC sensor (39)for detectingthe SOC of the battery(27); and wherein the controller(33) sets a lowerlimiting value permitted for the SOC of the battery; and activates thefuel cell without reference to the energy required for the activation ofthe fuel cell(21) when the detected SOC is less than or equal to thelower limiting value.
 8. A fuel cell power plant for a mobile unit, themobile unit provided with a drive device(29) driving the mobile unitwhen supplied with electrical power, the power plant comprising: a fuelcell(21) generating power when supplied with fuel; a battery(27) chargedwith power generated by the fuel cell; a power regulation device(31)selectively distributing power from the fuel cell and the battery to thedrive device; a controller(33) functioning to determine a short-termoperation running mode or a normal running mode; activate the fuel cellwhen a normal running mode is determined from the determination result;and control the fuel cell and the power regulation device so that thefuel cell is not activated and power from the battery is supplied to thedrive device when the short-term operation running mode is determined.9. The power plant as defined in claim 8, further comprising at leastone of a timer(33) for measuring the time after starting the powerplant; a sensor(38) for detecting the vehicle running speed; asensor(37) for detecting the depression amount of the accelerator pedal;a sensor(37) for detecting the depression speed of the acceleratorpedal; a sensor(39) for detecting the SOC of the battery; and whereinthe controller(33) determines the short-term operation running mode orthe normal running mode based on at least one of the detection values.10. The power plant as defined in claim 9, wherein the controller(33)determines the normal running mode when any one of the followingconditions are satisfied: when the measured time is long, when thevehicle speed is high, when the accelerator pedal depression amount islarge, when the speed of depressing the accelerator pedal is high orwhen the power consumption by the battery is large.
 11. The power plantas defined in claim 8, further comprising a calendar(57A) measuring thedate; a clock(57B) measuring the time; a GPS(57C) measuring position;and wherein the controller(33) uses a learning control routine to storea date/time pattern of the vehicle by combining the output values fromone or more of the above components; and determines the normal runningmode or the short-term operation running mode based on any one currentoutput value in the stored date/time running pattern.
 12. A fuel cellpower plant for a mobile unit, the mobile unit provided with a drivedevice(29) driving the mobile unit when supplied with electrical power,the power plant comprising: a fuel cell(21) generating power whensupplied with fuel; a battery(27) charged with power generated by thefuel cell; a power regulation device(31) selectively distributing powerfrom the fuel cell and the battery to the drive device; a switch(51)allowing selection of a normal running mode or a short-term operationrunning mode; and a controller(33) functioning to control the fuel celland the power regulation device so that the fuel cell is not activatedand power from the battery is supplied to the drive device when theshort-term operation running mode is selected.
 13. The power plant asdefined in claim 12, wherein the controller(33) both activates the fuelcell(21) and controls the power regulation device(31) so that power fromthe battery(27) is supplied to the drive device(29) when the normalrunning mode is selected.
 14. The power plant as defined in claim 12,further comprising a sensor for detecting the SOC of the battery(39);and wherein the controller(33) determines whether or not to activate thefuel cell(21) based on the detected residual charge in the battery whenthe short-term operation running mode is selected.
 15. The power plantas defined in claim 14, wherein the controller(33) activates the fuelcell(21) even when the short-term operation running mode is selected ifthe detected residual battery charge is low.
 16. A fuel cell power plantfor a mobile unit, the mobile unit provided with a drive device(29)driving the mobile unit when supplied with electrical power, the powerplant comprising: a fuel cell(21) generating power when supplied withfuel; a battery(27) charged with power generated by the fuel cell; asensor(39) for detecting the SOC of the battery; a power regulationdevice(31) selectively distributing power from the fuel cell and thebattery to the drive device; a switch(51) allowing selection of a normalrunning mode or a short-term operation running mode; and acontroller(33) functioning to estimate the energy required to activatethe fuel cell; estimate the time until completion of activation based onthe energy required to activate the fuel cell; estimate the powerconsumption during vehicle operation until the estimated time for fuelcell activation elapses; control the fuel cell and the power regulationdevice so that the fuel cell is not activated and power from the batteryis supplied to the drive device when the short-term operation runningmode is selected if the residual battery charge is greater than theestimated power consumption; and activate the fuel cell even when theshort-term operation running mode is selected if the residual batterycharge is less than the estimated power consumption.
 17. The power plantas defined in claim 16, further comprising a device performing voicedisplay or visual display(55); and wherein the controller(33) at leastnotifies the driver by a voice display or visual display that the fuelcell(21) is being activated or that activation has been completed, whenthe short-term operation running mode is selected